590 



SCIENCE. 



[N. S. Vol. XX. No. 514. 



and that mathematics, instead of giving us 

 any support for the supposition that it can, 

 carries us, by the processes of symboliza- 

 tion and formal implication to recognize 

 that logic must ultimately find its field 

 where implications are real, independent 

 of the processes by which they are thought, 

 and irrespective of the conceptions we 

 choose to frame. 



II. 

 The processes involved in the acquisition 

 and systematization of knowledge may, un- 

 doubtedly, be regarded as mental processes 

 and fall thus within the province of psy- 

 chology. It may be claimed, therefore, 

 that every logical process is also a psycho- 

 logical one. The important question is, 

 however, is it nothing more 1 Do its logical 

 and psychological characters simply coin- 

 cide? Or, to put the question in still an- 

 other form, as a psychological process 

 simply, does it also serve as a logical one? 

 The answers to these questions can be de- 

 termined only by first noting what psychol- 

 ogy can say about it as a mental process. 

 In the first place, psychology can analyze 

 it, and so determine its elements and their 

 connections. It can thus distinguish it 

 from all other mental processes by pointing 

 out its unique elements or their unique and 

 characteristic connection. No one will 

 deny that a judgment is different from an 

 emotion, or that an act of reasoning is 

 different from a volition; and no one will 

 claim that these differences are entirely 

 beyond the psychologist's power to ascer- 

 tain accurately and precisely. Still fur- 

 ther, it appears possible for him to deter- 

 mine with the same accuracy and precision, 

 the distinction in content and connection 

 between processes which are true and those 

 which are false. For, as mental processes, 

 it is natural to suppose that they contain 

 distinct differences of character which are 

 ascertainable. The states of mind called 

 belief, certainty, conviction, correctness. 



truth are, thus, doubtless all distinguish- 

 able as mental states. It may be admitted, 

 therefore, that there can be a thorough- 

 going psychology of logical processes. 



Yet it is quite evident to me that the 

 characterization of a mental process as 

 logical is not a psychological characteriza- 

 tion. In fact, I think it may be claimed 

 that the characterization of any mental 

 process in a specific way, say as an emotion, 

 is extra-psychological. Judgments and in- 

 ferences are, in short, not judgments and 

 inferences because they admit of psycho- 

 logical analysis and explanation, any more 

 than space is space because the perception 

 of it can be worked out by genetic psy- 

 chology. In other words, knovi'ledge is first 

 knowledge and only later a set of processes 

 for psychological analysis. That is why, as 

 it seems to me, all psychological logics, 

 from Locke to our own day, have signally 

 failed in dealing with the problem of 

 knowledge. The attempt to construct 

 knowledge out of mental states, the rela- 

 tions between ideas, and the relation of 

 ideas to things, has been, as I read the his- 

 tory, decidedly without profit. Confusion 

 and divergent opinion have resulted instead 

 of agreement and confidence. On precisely 

 the same psychological foundation, we have 

 such divergent views of knowledge as ideal- 

 ism, phenomenalism and agnosticism with 

 many other strange mixtures of logic, psy- 

 chology and metaphysics; The lesson of 

 these perplexing theories* seems to be that 

 logic, as logic, must be divorced from psy- 

 chology. 



It is also of importance to note, in this 

 connection, that the determination of a pro- 

 cess as mental and as thus falling within 

 the domain of psychology strictly, has by 

 no means been worked out to the general 

 satisfaction of psychologists themselves. 

 Recent literature abounds in elaborate dis- 

 cussion of the distinction between what is 

 a mental fact and what not, with a pre- 



